Hi Prince,
Please follow the Next Steps to help troubleshoot:
1.Please double check if the SNMP string/password/setting entered in the Network Setting is correct.
2..Login to the Front Server and test the SNMP access to the device with the same credential Netbrain uses.
If it is a Windows Server, you can try the SNMPwalk tool in this link.
If it is a Linux Server, you can try the snmpwalk command.
3.If step 1and2 checks fine, you can try to increase the SNMP timeout value in Domain Management > Operations > Domain Settings > Advanced Settings and try again
4.If all the above are verified and SNMP still failed for the device, please submit a ticket to Netbrain Support.
Thanks!